docs: def download(self, filename, output, packethook=None, timeout=SOCK_TIMEOUT):
          """This method initiates a tftp download from the configured remote
          host, requesting the filename passed. It writes the file to output,
          which can be a file-like object or a path to a local file. If a
          packethook is provided, it must be a function that takes a single
          parameter, which will be a copy of each DAT packet received in the
          form of a TftpPacketDAT object. The timeout parameter may be used to
          override the default SOCK_TIMEOUT setting, which is the amount of time
          that the client will wait for a receive packet to arrive.
  
          Note: If output is a hyphen, stdout is used."""
          # We're downloading.
          log.debug("Creating download context with the following params:")
          log.debug("host = %s, port = %s, filename = %s" % (self.host, self.iport, filename))
          log.debug("options = %s, packethook = %s, timeout = %s" % (self.options, packethook, timeout))
          self.context = TftpContextClientDownload(self.host,
                                                   self.iport,
                                                   filename,
                                                   output,
                                                   self.options,
                                                   packethook,
                                                   timeout,
                                                   localip = self.localip)
          self.context.start()
          # Download happens here
          self.context.end()
  
          metrics = self.context.metrics
  
          log.info('')
          log.info("Download complete.")
          if metrics.duration == 0:
              log.info("Duration too short, rate undetermined")
          else:
              log.info("Downloaded %.2f bytes in %.2f seconds" % (metrics.bytes, metrics.duration))
              log.info("Average rate: %.2f kbps" % metrics.kbps)
          log.info("%.2f bytes in resent data" % metrics.resent_bytes)
          log.info("Received %d duplicate packets" % metrics.dupcount)